1. Field of the Invention
The present invention relates to systems and methods for controlling the volume of an audio output, and particularly to a system and method for controlling volume according to the rotational direction and speed of a single manually operated knob.
2. Background of the Invention
Presently, there are many audio output apparatuses for amplifying audio signals of loudhailers. These audio output apparatuses are known as “audio frequency amplifier apparatus,” and are used to adjust the output voltage of the loudhailers according to manual adjustment operations and corresponding adjustment commands. Conventional audio output apparatuses provide a single knob for adjusting volume, and a separate muting key for muting the volume.
One kind of audio output apparatus for digitally adjusting volume comprises a rotation adjustor and a rotation encoder. The rotation adjustor is for manual rotation by a user. The rotation encoder is for outputting information indicating the direction of rotation, and supplying the information together with an output pulse to a microcomputer for generating a volume adjustment signal. The microcomputer determines the direction of the adjustment (i.e., upward or downward) on the basis of the information indicating the direction of the rotation obtained from the rotation encoder, and supplies a unit amount of change in volume per one pulse as a volume adjustment signal. For example, each time one pulse is received from the rotation encoder, the microcomputer determines the rotational speed by measuring the cycle of pulses from the rotation encoder, and alters the unit change in volume per one pulse as a volume adjustment signal. For example, when the rotational speed is high, the unit change in volume is increased corresponding to the rotational operation. Because the alteration to the unit change in volume corresponds linearly with the rotational speed, it is difficult to rapidly make adjustments from a very high volume to a very low volume, and vice-versa. The user ends up having to spend more time in making adjustments.
There is nothing known in the art which can efficiently and rapidly effect large adjustments to volume during high-speed rotation of a single knob of a volume controlling apparatus.